The present invention relates to the medical diagnostic and surgical arts. It finds particular application in conjunction with stereotactic surgery and will be described with particular reference thereto. It will be appreciated, however, that the invention will also find application in conjunction with minimally invasive surgery, neurosurgery, neurobiopsy, CT-table needle body biopsy, breast biopsy, endoscopic procedures, orthopedic surgery, other invasive medical procedures, industrial quality control procedures, and the like.
Three-dimensional diagnostic image data of the brain, spinal cord, and other body portions is produced by CT scanners, magnetic resonance imagers, and other medical diagnostic equipment. These imaging modalities typically provide structural detail with a resolution of a millimeter or better.
Various frameless stereotactic procedures have been developed which take advantage of the three-dimensional image data of the patient. These procedures include guided-needle biopsies, shunt placements, craniotomies for lesion or tumor resection, and the like. Another area of frameless stereotaxy procedure which requires extreme accuracy is spinal surgery, including screw fixation, fracture decompression, and spinal tumor removal.
In one prior art technique, the fiducials or other markers which are imaged substantially as points in the diagnostic imaging process are affixed to the patient's head or other stable region of interest before the image data is generated. In this manner, the fiducials appear as points in the resultant image data. Before the frameless stereotaxy procedure, a pointer is touched to each of the fiducials and actuated to generate a position indicating signal. By touching the pointer to several fiducials and actuating it, a plurality of points corresponding to the fiducials are determined in the coordinate system of the pointer, operator space. The coordinates of the fiducials are readily identified in the coordinate system of the diagnostic data. As illustrated in U.S. Pat. No. 5,309,913, once a plurality of corresponding coordinates are known in two different coordinate systems, the mathematical transform for transforming coordinates of one coordinate system into the other is readily calculated.
For some medical procedures, the use of fiducials is inconvenient or inappropriate. For example, in spine surgery, the spine is separated from the outer surface of the skin by muscle and fat tissue. Accordingly, fiducials affixed to the skin during an imaging procedure are apt to shift relative to the spine, when the patient moves. However, the spine itself has many small, distinctive structures, such as points that are readily identified in the diagnostic image. Once the surgery is started and the spine is exposed, the pointer is positioned on these distinctive structures and actuated to mark the structures in the pointer coordinate system. The corresponding points in the diagnostic image are identified and their coordinates determined. In this manner, natural, anatomical fiducials are used instead of artificial fiducials. They are again imaged in a fixed relationship to the region of interest during the imaging procedure.
However, there are other regions of the anatomy, such as the organs, to which fiducials cannot be attached conveniently and which lack pointer accessible, accurate anatomical fiducials or marker points.
The present invention provides a new and improved apparatus and method which overcomes the above-referenced problems and others.